JP2002122572A - Method and apparatus for evaluation of material characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus, for the evaluation of a material characteristic, wherein the material characteristic can be evaluated in a short time and with high accuracy by a Hall sensor by a method wherein, since the material characteristic of a specimen is evaluated on the basis of the differential value of a leakage flux value which is in a correlation with the differential value of the residual stress of the specimen, the characteristic of the material can be evaluated with a compact constitution and with high accuracy, the distribution of the differential value of the leakage flux value can be visualized and used and the evaluation of the material characteristic can be judged instantaneously. SOLUTION: In the evaluation method for the material characteristic contains a measuring process in which leakage flux values in a plurality of prescribed positions of the specimen are measured by the Hall sensor, a magnetic-flux-distribution calculation process in which the leakage flux distribution of the specimen is found on the basis of the leakage flux values in the plurality of positions, a differential-value calculation process in which a differential value in a direction parallel to the measuring plane of the leakage flux distribution is calculated so as to find the plane distribution of the differential value and an evaluation process in which the material characteristic of the specimen is evaluated on the basis of the plane distribution of the differential value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for evaluating characteristics such as residual stress level, fatigue damage degree, irradiation damage degree, and thermal embrittlement degree of a material by a nondestructive inspection technique. The present invention relates to an evaluation method and an apparatus using a sensor.

[0002]

2. Description of the Related Art Non-destructive inspection techniques for evaluating various material properties are being developed. When the nondestructive inspection method is used, the spatial resolution of evaluation largely depends on the minimum area that can be evaluated, specifically, mainly, the size of a sensor to be used. For this reason, a sensor having a smaller size is required to improve the spatial resolution. On the other hand, if you need to evaluate an entire area using a small sensor,
Since the inspection object has to be scanned and evaluated for more time, a sensor that can easily perform the scanning measurement is required.

An X-ray residual stress measurement method has been generally known as an industrially established technique capable of nondestructively measuring material properties, particularly the residual stress level during processing of the material. In the X-ray residual stress measurement method, since the stress of a material is based on the minute deformation of crystal grains, the residual stress is calculated by transmitting the X-ray to the test material and measuring the displacement of the lattice points of the crystal. It is. The X-ray residual stress measurement method is excellent in that the measurement result has high reliability, and a transportable measuring device using the X-ray residual stress measurement method is generally known.

[0004]

However, in order to emit X-rays, the size of the apparatus becomes excessively large and the weight is large. For this reason, there is a problem that the measuring device cannot be installed in a place where the measurement place is narrow and space is limited.
In addition, because of its heavy weight, it takes too much labor to transport and install it even in a large place. Furthermore, such an X-ray residual stress measuring device cannot be used in water.

Although it is possible to measure the residual stress by narrowing the X-ray beam to about 1 mm, it takes more time to evaluate the test object when evaluating the entire region of the test object. The need to scan and evaluate arises, X
There is a problem that it is difficult to scan the line residual stress measuring device with high accuracy due to its size, weight, and the like.

Further, since the X-ray residual stress measurement method is a measurement method using radiation, there is a problem that the measurement becomes difficult in a place having a high radiation background.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and an object of the present invention is to provide a material property evaluation method and apparatus capable of accurately evaluating the material properties of a test object with a compact apparatus configuration. Main purpose. Another object of the present invention is to provide a material property evaluation method and apparatus capable of evaluating the material properties of an inspection object in a short time with high accuracy.

[0008]

According to a first aspect of the present invention, there is provided a measuring apparatus for measuring a leakage magnetic flux value at a plurality of predetermined positions on a test material using a Hall sensor. A magnetic flux distribution calculating step of calculating a leak magnetic flux distribution of the test material from a leak magnetic flux value at a position, calculating a differential value of the leak magnetic flux distribution in a direction parallel to a measurement plane, and calculating a differential value calculating a differential value plane distribution; And a step of evaluating a material property of the test material based on the planar distribution of the differential value.

In the first aspect of the present invention, a Hall sensor is used as a sensor for evaluating material characteristics.
The Hall sensor utilizes a compact Hall element, and is an electronic device using the Hall effect. Here, the Hall effect is an effect that, when a magnetic field is applied in a direction perpendicular to the current direction of a metal or semiconductor, an electromotive force is generated in a direction perpendicular to the two. A Hall sensor uses such a Hall effect to improve the magnetic characteristics. It is to be inspected. That is, a sample as an object to be inspected is approached immediately below the Hall element while the Hall element is energized, and the Hall voltage generated by the magnetic flux detected at this time is measured. Since the Hall voltage has linearity that is proportional to the product of the current and the magnetic flux density, the magnetic flux density can be measured from the measured Hall voltage and the current value. Normally, the Hall element has a size of about 120 μm square, and a smaller element has been researched and developed.

Further, according to the present invention, the inventors have found that the differential value of the leakage magnetic flux of the test material in a direction parallel to the measurement surface corresponds to the differential value of the residual stress of the test material. This is applied to material property evaluation.

FIGS. 3 and 4 show the distribution of the differential value | dσ _x / dx | of the residual stress value when plastic strain is applied to a tensile test piece made of A533B steel. FIG.
FIG. 4 shows the case of a plastic strain of 7.35%, and FIG.
This is the case of 8% plastic strain. 3 and 4, the horizontal axis represents the position in the x direction from the center of the measurement area of the test material (A533B steel), and the vertical axis represents the differential value | dσ of the residual stress.
_x / dx |. Here, σ _x is the longitudinal direction (x direction) of the tensile test piece measured by the X-ray residual stress measuring device.
, And dσ _x / dx indicates a differential value of the measured residual stress value in the x direction.

On the other hand, FIG. 5 and FIG. 6 are measured in FIG. 3 and FIG.
Differential value of leakage magnetic flux of fixed tensile test piece | dB_z/ Dx
| Is shown. Figure 5 shows 7.35% plastic strain
And corresponds to FIG. FIG.
8% plastic strain, corresponding to FIG.
You. 5 and 6, the horizontal axis represents the test material (A533B).
Steel) in the x direction from the center of the measurement area, and the vertical axis indicates
Leakage magnetic flux differential value | dB _z/ Dx |. here
And B_zIs the vertical surface of the tensile test specimen measured by the Hall sensor.
Indicates the leakage magnetic flux value in the direct direction (z direction), and_z/ Dx
Indicates the derivative of the measured leakage flux value in the x direction.
You.

3 and 5, and FIGS. 4 and 6, respectively.
The differential value of residual stress | dσ _x/ Dx | and leakage magnetism
Derivative of bundle value | dB_z/ Dx | distribution is very close
Similar, with good correlation between the two
You can see that. That is, the residual stress value in the longitudinal direction of the tensile test piece
Differential value in the longitudinal direction (x direction) | dσ_x/ Dx |
Magnetic flux value in the vertical direction (z direction) on the surface of the tension test piece | dB
_z/ Dx | clearly corresponds to
I was sent out. Generally, as the dislocation density increases, the material becomes magnetized.
A533B
The distribution of magnetic flux leakage generated by steel is
Lattice defects such as dislocation structures in the structure change, and as a result
Attributed to the change in permeability (permeability)
Can be

In the present invention, the leakage magnetic flux values at a plurality of positions are measured by the Hall sensors in such a measuring step, the leakage magnetic flux distribution of the test material is obtained from the leakage magnetic flux values measured in the magnetic flux distribution calculating step, and the differential value is calculated. In the process, the differential value of the leakage flux distribution in the direction parallel to the measurement plane is calculated, the plane distribution of the differential value is obtained, and the correlation between the distribution of the differential value of the residual stress and the distribution of the differential value of the leakage magnetic flux value is used. Since the material properties are evaluated in the evaluation step, the evaluation can be performed with high accuracy using a Hall sensor and a compact device configuration.

The contents of the evaluation in the present invention include, for example, evaluation of whether the stress field on the material surface is uniform, whether there is a local discontinuous region, and the like. Here, in the present invention, a plane distribution of differential values is obtained by a differential value calculating step,
Since the state of distribution of the differential value is visualized, such evaluation can be determined instantaneously, and highly accurate material property evaluation can be performed in a short time.

In the evaluation step in the present invention, any method may be used as long as it generates a planar distribution of the differential value of the leakage magnetic flux value. For example, the evaluation step is displayed or output in a graph as shown in FIG. 5 or FIG. It is also possible to display or output in a format. Furthermore, the distribution status of the differential value of the leakage magnetic flux value may be displayed or output in different colors. In this case, there is an advantage that the distribution state of the differential value of the leakage magnetic flux value can be determined in a shorter time by the color-coded display.

In the evaluation of the material properties in the present invention, in addition to the evaluation of the properties that change the magnetic properties, that is, the evaluation of the residual stress level of the material, the evaluation of the degree of fatigue damage, the degree of irradiation damage, the degree of thermal embrittlement, etc. Is included.

In the measuring step of the present invention, a plurality of positions of the test material to be measured by the Hall sensor can be arbitrarily determined. However, if the leakage magnetic flux is measured at positions at short distance intervals, a more accurate evaluation result can be obtained. Can be obtained.

According to a second aspect of the present invention, there is provided a Hall sensor for measuring a leakage magnetic flux of the test material, a moving means for moving the Hall sensor along the surface of the test material, and A magnetic flux distribution calculating means for calculating a leakage magnetic flux distribution of the test material from a leakage magnetic flux value at a plurality of positions; a differential value for calculating a differential value of the leakage magnetic flux distribution in a direction parallel to a measurement plane to obtain a plane distribution of the differential value; The present invention relates to a material property evaluation device, comprising: a calculation unit; and an output unit that outputs a plane distribution of a differential value of the leakage magnetic flux value. The present invention is an apparatus for carrying out the method according to the first aspect, and has the same effect as the first aspect.

The output means in the present invention may be any as long as it outputs a plane distribution of the differential value of the leakage magnetic flux value. For example, a display device, a printer device or the like may be used.
Further, an evaluation means for evaluating the material properties of the test material based on the planar distribution of the leakage magnetic flux differential value may be further provided to automatically determine and evaluate the material properties. In this case, complete automation can be achieved, which is convenient for the inspector.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a material property evaluation method and apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. In the present embodiment, the present invention is applied to a residual stress measurement device and a residual stress evaluation method for evaluating a residual stress characteristic of a sample 21 as a test material. FIG. 1A is an overall configuration diagram of the residual stress measurement device of the present embodiment. As shown in FIG. 1A, a residual stress measuring device according to the present embodiment includes a Hall sensor 1 for measuring a magnetic flux value of a test material, an arm 5 to which the Hall sensor 1 is attached, and a parallel to the surface of the test object. An XY position controller 3 for moving the Hall sensor 1 in the x-axis direction and the y-axis direction, and a computer 9 connected to the XY position controller 3 are mainly provided.

FIG. 1B is a block diagram showing a functional configuration of the computer 9. As shown in FIG. 1B, a computer 9 connected to the XY position controller 3 receives an input control unit 11 for inputting a leakage magnetic flux value measured by the Hall sensor 1 and performs a test based on the input leakage magnetic flux value. Magnetic flux distribution calculating unit 13 for calculating the leakage magnetic flux distribution of the material
A differential value calculator 15 for calculating a differential value of the calculated leakage magnetic flux distribution in the x direction parallel to the measurement plane to obtain a planar distribution of the differential value, and a display unit for displaying the planar distribution of the differential value of the leak magnetic flux. 17 and an output unit 19 for outputting the plane distribution
And the main. Here, the XY position controller 3 and the arm 5 constitute a moving unit of the present invention, and the display unit 17 and the output unit 19 constitute an output unit of the present invention.

A sample 21 (tensile test piece) of the test material is
A predetermined plastic strain is given. In the present embodiment, the sample
A533B steel having the shape shown in FIG.
(Wt%) C: 0.18, Si: 0.14, Mn: 1.53, P: 0.004, S: 0.0
02, Cu: 0.03, Ni: 0.66, Mo: 0.56, Al: 0.01, Fe: bal.)
7.35% plasticity for this A533B steel
Distortion was applied in advance. The material of the sample 21 is A5
It is not limited to 33B steel. Also attached to sample 21
The distortion to be applied is not limited to 7.35%.
Here, A533 to which the plastic strain of 7.35% is applied
For steel B, a 1 mmφ collimator was used as shown in FIG.
With respect to the measurement area 23 indicated by the oblique line, the x-direction (longitudinal direction)
X-ray residual stress value σ_xAnd measure the residual stress value in the x direction.
Value | dσ _x/ Dx | distribution was determined. Figure 3
Differential value of residual stress | dσ_x/ Dx | distribution map
You. FIG. 4 shows that the A533B steel has a plastic strain of 0.38%.
Differential value of residual stress value when applied | dσ_x/ Dx |
It is a distribution map. Sample 21 (A533B steel) is a current source
(Not shown), and is passed in a predetermined x direction in advance.
Is being charged.

The Hall sensor 1 has a commercially available Hall element of about 120 μm square mounted at its tip. The current terminal of the Hall element is connected to a current source (not shown) for the Hall element, and is in a conducting state. The current direction in the Hall element is in the y direction, and therefore, the electromotive force is generated in the z direction orthogonal to the x direction and the y direction by the Hall effect. A voltmeter (not shown) is connected to the Hall terminal of the Hall element, so that the Hall voltage generated by the magnetic flux from the sample 21 is measured. The measured voltage value as the magnetic flux value B _z in the z-direction, are input to the input control unit 11 of the computer 9 together with the position coordinates of the measurement point.

The XY position controller 3 moves the Hall sensor 1 fixed to the arm 5 in the x direction within the measurement area 23, whereby the Hall sensor 1 scans (scans) the surface of the sample 21 in parallel, at a predetermined interval. The leakage magnetic flux is measured every time.

The magnetic flux distribution calculation unit 13 is constituted by a program operating on the computer 9 and calculates the leakage magnetic flux distribution of the sample 21 from the value of the leakage magnetic flux on the sample surface and the position coordinates of the measurement point input by the input control unit 11. It is.

The differential value calculator 15 is composed of a program operating on the computer 9 and calculates the differential value | dB _z / dx | in the x direction at each measurement point from the leakage magnetic flux distribution of the sample 21 obtained by the magnetic flux calculator. This is to calculate the differential value distribution of the magnetic flux values as shown in FIG. 5 or FIG. 6, for example.

The display unit 17 is, for example, a display device or the like, and the output unit 19 is a printer device or the like, and the differential value in the x direction | dB _z /
dx |.

Next, a description will be given of a residual stress evaluation method using the residual stress measuring device of the present embodiment configured as described above. FIG. 2 is a flowchart of the residual stress evaluation method of the present embodiment.

First, the sample 21 (A533B steel) is set on the table 7 of the XY position controller 3 to energize the sample 21 in advance, and the Hall element of the Hall sensor 1 is also energized in advance (step 201). Then, while driving the XY position controller 3, the Hall sensor 1 scans the measurement area 23 on the sample surface in the x direction,
measuring the magnetic flux value _{B z} in the z-direction from the sample 21 in μm intervals (step 202). The measured magnetic flux value _Bz is sequentially transferred to the input control unit 11 of the computer 9 together with the position coordinates of the measurement point. Here, in the present embodiment, the measurement interval is 250 μm, but is not limited to this, and can be arbitrarily determined according to various conditions such as the size of the Hall element and the measurement area.

In the computer 9, the magnetic flux distribution calculator 13
By, corresponding to generate a leakage magnetic flux distribution of the sample 21 to the leakage flux value B _z of the input sample surface and the position coordinates of the measurement point (step 203). Then, the differential value calculation unit 1
5, a differential value | dB _z / dx | of the magnetic flux value at each measurement point in the x direction is calculated from the leakage magnetic flux distribution of the sample 21 generated by the magnetic flux calculation unit (step 204), and FIG.
Differential value as shown in _| dB z / dx _| generates a distribution (Step 205). When a plastic strain of 0.38% is applied to the sample 21, a distribution diagram shown in FIG. 6 is generated.

The x-direction differential value | dB _z / dx | of the magnetic flux value generated by the differential value calculation unit 15 is displayed on the display unit 17 and / or displayed on the output unit 19 in response to a command from the examiner (step). 206). As a result, the distribution of the differential value | dB _z / dx | of the magnetic flux value is visualized and displayed and output in a format that can be viewed by the inspector.

5 and FIG. 3 (or FIG. 6 and FIG. 4), the distribution of the differential value (FIG. 5 or FIG. 6) of the leakage magnetic flux value | dB _z / dx | To sample 2
1 | dσ _x
/ Dx | distribution (FIG. 3 or FIG. 4), and it can be seen that there is a correlation with each other. Thus, the differential value of the display or output magnetic flux value | dB z / _dx | based on plan distribution diagram, to evaluate the residual stress characteristics of a sample 21 (step 207). For example, based on a planar distribution diagram of the differential value of the leakage magnetic flux, it is determined that the residual stress is uniform in a distribution state in which the differential value of the leakage magnetic flux is uniform. On the other hand, in the case of a distribution state in which the leakage magnetic flux differential value is locally discontinuous, it is determined that the residual stress value changes abruptly at the discontinuous portion.

FIG. 8 shows A53 as the sample 21.
A 1.4% residual strain was imparted to the 3B steel, and the measurement area 2
3 is scanned by the Hall sensor 1 in the x direction, the leakage magnetic flux value is measured at intervals of 250 μm, and the leakage magnetic flux differential value | dB _z / dx
| Are visualized and displayed and output in a form different from that of FIG. 5 or FIG. 8, the horizontal axis indicates the position in the x direction from the left end of the measurement area 23 in FIG. 7, and the vertical axis indicates the differential value of the leakage magnetic flux. In the actual output result of FIG. 8, color display is performed. The portion is displayed in red to indicate that the leakage flux value is a positive value, and the portion is displayed in blue to indicate that the leakage flux value is a negative value. , Are displayed in black to indicate that the leakage magnetic flux value is zero. As can be seen from the distribution diagram in FIG. 8, a band (shown in blue) appears on the left side from the center. Observation of the surface of the sample 21 indicated that the portion corresponded to the Luder's band generated during the tensile test. Thus, from the change in the differential value of the leakage magnetic flux, it is possible to identify a unique part called the Ruder's band from the sample 21.
It is possible to instantaneously detect a portion where the stress field changes in the sample 21 from a change in the differential value of the leakage magnetic flux.

[0035] In this way, residual stress measuring system and residual stress evaluation method of the present embodiment, by measuring the leakage flux value B _z at a plurality of measurement positions Compact Hall sensors 1,
From the leakage flux value _Bz measurement result, the differential value of residual stress |
Since the residual stress characteristic of the sample 21 is evaluated by obtaining a plane distribution diagram of a differential value | dB _z / dx | in the x direction parallel to the measurement plane of the leakage magnetic flux distribution correlated with dσ _x / dx | The highly accurate material characteristics of the sample 21 can be evaluated with a compact apparatus configuration. In the residual stress measuring device and the residual stress evaluation method of the present embodiment, the differential value | dB _z
/ Dx | is obtained and displayed on the display unit 17 and output to the output unit 19 in a visualized state, so that the inspector can instantaneously judge the evaluation of the residual stress characteristics. It is possible to perform highly accurate residual stress evaluation in a short time.

In the residual stress measuring apparatus of the present embodiment, the computer 9 is further provided with an evaluation unit for evaluating the residual stress characteristics of the sample 21 based on the planar distribution of the leakage magnetic flux differential value | dB _z / dx | The configuration may be such that the residual stress characteristics are automatically evaluated and output.

In the present embodiment, the present invention is applied to the evaluation of the residual stress characteristics. However, the present invention can be applied to any evaluation as long as the magnetic characteristics of the sample 21 are changed. The present invention may be applied to the evaluation of the degree of fatigue damage, the degree of irradiation damage, the degree of thermal embrittlement, and the like.

The residual stress measuring apparatus and the residual stress evaluation method according to the present embodiment evaluate residual stress characteristics on a tensile test piece as a test material (sample), that is, perform evaluation at a laboratory level. However, it goes without saying that the evaluation of the material properties can be performed on a test material at a practical level such as a flat plate structure or a pipe structure as a measurement target. In this case, X
In place of the Y position controller 3, a flat plate structure,
A drive mechanism capable of positioning and scanning (scanning) the test material such as a pipe structure may be provided.

[0039]

As described above, according to the present invention,
Since the material properties of the test material are evaluated based on the differential value of the leakage magnetic flux value that has a correlation with the differential value of the residual stress of the test material,
This has the effect that the characteristics of the material can be evaluated with high accuracy with a compact configuration. Further, the distribution of the differential value of the leakage magnetic flux value can be visualized and used, and the evaluation of the material characteristics can be judged instantaneously, so that the material characteristics can be evaluated with high accuracy in a short time.

[Brief description of the drawings]

FIG. 1A is a configuration diagram of a residual stress measurement device of the present embodiment, and FIG. 1B is a block diagram illustrating a functional configuration of the computer.

FIG. 2 is a flowchart of a residual stress evaluation method of the present embodiment.

FIG. 3 is a distribution diagram of a differential value of a residual stress value when a plastic test of 7.35% is applied to a tensile test piece made of A533B steel in the present embodiment.

FIG. 4 is a distribution diagram of a differential value of a residual stress value when a plastic strain of 0.38% is applied to a tensile test piece made of A533B steel in the present embodiment.

FIG. 5 is a diagram illustrating a tensile test piece according to the present embodiment.
It is a distribution diagram of the differential value of the leakage magnetic flux value at the time of giving 35% of plastic strain.

FIG. 6 is a graph showing the relationship between a tensile test piece and a tensile test piece according to the embodiment;
FIG. 10 is a distribution diagram of differential values of leakage magnetic flux values when a plastic strain of 38% is applied.

FIG. 7 is a plan view of an A533 steel test piece evaluated in the present embodiment.

FIG. 8 is an explanatory diagram showing a distribution state of a differential value of a leakage magnetic flux value in a central portion of an A533 steel test piece obtained in the present embodiment.

[Explanation of symbols]

 1: Hall sensor 3: XY position controller 5: Arm 7: Table 9: Computer 11: Input control unit 13: Magnetic flux distribution calculation unit 15: Differential value calculation unit 17: Display unit 19: Output unit 21: Sample (test material) ) 23: Measurement area

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinsuke Yamanaka 14-5-401 Asahigaoka-cho, Ashiya-shi, Hyogo (72) Inventor Yoshihiro Isobe 3-323-1-201 Okubokita, Kumatori-cho, Sennan-gun, Osaka F term (reference) 2G053 AA11 AA14 AA19 AB22 BA21 CA05 CA18

Claims (2)

[Claims] 1. A measuring step of measuring leakage magnetic flux values at a plurality of predetermined positions of a test material by a Hall sensor, and a magnetic flux distribution calculating step of obtaining a leakage magnetic flux distribution of the test material from the leakage magnetic flux values at the plurality of positions. A differential value calculation step of calculating a differential value of the leakage magnetic flux distribution in a direction parallel to the measurement plane and obtaining a planar distribution of the differential value; based on the planar distribution of the differential value, And a step of evaluating the material properties. 2. A Hall sensor for measuring a leakage magnetic flux of a test material, a moving means for moving the Hall sensor along a surface of the test material, and a leakage magnetic flux at a plurality of positions of the test material by the Hall sensor. A magnetic flux distribution calculating means for calculating a leakage magnetic flux distribution of the test material from the value; a differential value calculating means for calculating a differential value of the leakage magnetic flux distribution in a direction parallel to a measurement plane to obtain a plane distribution of the differential value; Output means for outputting a planar distribution of a differential value of a magnetic flux value.